Laminoplasty with laminar stabilization method and system

ABSTRACT

Fixation devices and methods for stabilization of the lamina after laminoplasty are described. The device comprises of a plate with several holes that receive bone fasteners. The plate is curved at the ends to contour to the vertebral structure and has appendages to engage the displaced lamina in a fixed position. Alternatively, the plate has a bone fusion spacer in the middle to engage and fuse the lamina in the displaced position. Several methods of dynamically stabilizing the lamina after either the open door, double door or expansive laminoplasty technique are provided.

BACKGROUND OF THE INVENTION

[0001] Cervical stenosis with spinal cord compression and consequentmyelopathy is a very common problem encountered by the spine surgeon.The usual cause of multilevel cervical stenosis is spondylosis and/orossification of the posterior longitudinal ligament. Surgicaldecompression either through an anterior or posterior approach can beundertaken.

[0002] An anterior approach usually involves multilevel corpectomy withfusion and stabilization. The main drawback of this technique is theincreased time and complexity of the procedure as well as the risk ofpseudoarthrosis and accelerated degeneration at the levels above andbelow the fusion.

[0003] A posterior approach has traditionally involved a simplelaminectomy, laminectomy with facet fusion, or more recentlylaminoplasty. The drawback of a simple laminectomy is the risk of lateclinical deterioration form either kyphosis or postlaminectomy scarformation. Laminectomy with facet fusion decreases the risk of kyphosisbut it also decreases the range of motion in the spine and increases therisk of accelerated degeneration at the levels above and below thefusion.

[0004] Laminoplasty either through open door or double door techniquedeveloped more recently provides greater stability and range of motionwhen compared with laminectomy alone. This technique entailslaminoplasty for decompression with laminar fusion with allo- orautograft bone and/or fixation with a plate. The principle behindlaminar fusion and fixation is that it maintains the decompressionfollowing laminoplasty as well as the displaced lamina in a fixedposition thereby providing stabilization also.

[0005] U.S. Pat. No. 6,080,157 to Cathro et al. describes an implant tostabilize the lamina after laminoplasty. A major limitation of thisimplant and technique is that a single implant extends to all thelaminoplasty levels and is followed by posterior autograft fusionthereby disabling the inherent mobility between the cervical spinelevels which laminoplasty attempts to preserve.

[0006] The present invention is an apparatus for use in laminoplasty tofuse and stabilize the lamina individually in the cervical, thoracic orlumbar spine thereby preserving the range of motion as well as providingstability.

SUMMARY OF THE INVENTION

[0007] The present invention relates a laminar fusion and fixationsystem following laminoplasty. This system with the bone fusion spaceror resorbable fusion graft and plate reduces surgical time andsimplifies laminar fusion and fixation after laminoplasty.

[0008] The bone fusion spacer consists of a bicortical bone graft withvariable length but uniform width and thickness specific for thecervical, thoracic or lumbar spine. The edges are contoured with a notchto allow securement to the lamina on one side and the lateral mass orfacet on the other side.

[0009] In another embodiment of the bone fusion spacer, the edges have asuperior cuff or shoulder that allows securement against the lamina andfacet on either sides as well prevent migration of the bone graft intothe spinal canal.

[0010] The resorbable fusion graft has a design similar to the allograftbone graft but is made of hydroxyapatite or similar absorbable materialwhich is eventually resorbed and/or replaced with autologous bone duringthe fusion process.

[0011] The invention also comprises a plate made of titanium or similaralloy with magnetic resonance imaging compatibility of variablethickness which is contoured at the edges to allow fixation of thelaminoplasty and securement of the bone graft. The contoured design ofthe plate allows screw placement in the lamina or spinous process on oneside and the facet on the other side.

[0012] In another embodiment the allograft bone or resorbable graft andplate are constructed as a unit with the bone graft attached to theplate in the middle through either screws or an adhesive material.

[0013] In another embodiment, the bone graft and plate are designed forlaminar fusion and fixation following double door laminoplasty. The bonegraft in the middle allows for laminar fusion in the decompressedposition with the plate design bent on either end securing the graft tothe lamina and facet.

[0014] In another embodiment, the plate has appendages that engage thelamina and facet in a fixed position without the use of a bone spacer.

[0015] The procedure as would be undertaken with the use of thelaminoplasty fixation system is described as follows. An open doorlaminoplasty entails creating a gutter at the junction of the lamina andmedial aspect of the facet on both sides with the use of a drill. On theside of the laminoplasty opening, the drilling is carried through intothe canal or the opening completed with a small kerrison rongeur. At theother side, the inner cortex at the lamina and facet junction is notdrilled. The lamina at the open end is elevated and the spinous processpushed away in order to create a greenstick osteotomy and allow for thelaminoplasty decompression. Typically, atleast one centimeter ofdistraction between the lamina and the facet provides for a good spinaldecompression. In order to maintain the position of the lamina, thepre-contoured bicortical allograft of appropriate size is positionedbetween the lamina and the facet. Stabilization at each level is thenundertaken with placement of the pre-designed plate with the curved endsto allow one end to secure to the lamina with a screw and the other endto the facet. Alternatively, the bone graft pre-attached to the platecan also be used to provide laminar fusion in the fixed position. Insituations where laminoplasty stabilization without the use of a fusiongraft is desired, the plate with added appendages to secure thedisplaced lamina is used.

[0016] Another variation on the open door laminoplasty is the expansivelaminoplasty most suited for the thoracolumbar spine. In this method,the lamina on either side at the junction of the facets are drilled andopened. A lateral spinal canal recess decompression and/or foraminotomyis undertaken and the lamina replaced with bone graft/plate construct onboth sides.

[0017] A trap door or double door laminoplasty is created by drilling oneach side at the laminar and later mass junction the outer laminarcortex and sparing the inner laminar cortex. The spinous process isresected and a midline gutter is also created which extends through theinner cortex which can be opened with a small kerrison rongeur. Thelamina on either side are lifted and opened creating a greenstickosteotomy on each side. In order to maintain the decompressed positionof the lamina, a plate alone or a bone graft/plate construct is placed.The plate can either be fixated with screws to the lamina or the facets.For situations where laminar stabilization without the use of a fusiongraft is desired, the plate with appendages in the middle is used.

[0018] While the inventions described here are specific, any variationsto the described embodiments falls within the scope of the currentinvention and the protection granted therein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a cross section of the vertebra

[0020]FIG. 2 is a top view of the bone graft

[0021]FIG. 3 is a side view of one embodiment of the bone graft

[0022]FIG. 4 is a cross section of the vertebra following open doorlaminoplasty with one embodiment of the bone graft

[0023]FIG. 5 is a side view of another embodiment of the bone graft

[0024]FIG. 6 is a cross section of the vertebra following open doorlaminoplasty with another embodiment of the bone graft

[0025]FIG. 7 is a top view of one embodiment of the plate

[0026]FIG. 8 is a top view of another embodiment of the plate

[0027]FIG. 9 is a side view of the plates

[0028]FIG. 10 is a top view of the graft and plate construct

[0029]FIG. 11 is a side view of one embodiment of the construct

[0030]FIG. 12 is a cross section of the vertebra with the graft andplate construct in place

[0031]FIG. 13 is a side view of another embodiment of the construct

[0032]FIG. 14 is a cross section of the vertebra with the graft andplate construct in place

[0033]FIG. 15 is a cross section of the vertebra with expansivelaminoplasty

[0034]FIG. 16 is a cross section of the vertebra following double doorlaminoplasty with one embodiment of the bone graft

[0035]FIG. 17 is a cross section of the vertebra following double doorlaminoplasty with another embodiment of the bone graft

[0036]FIG. 18 is a top view of one embodiment of the graft and plateconstruct

[0037]FIG. 19 is a side view of the construct

[0038]FIG. 20 is a cross section of the vertebra with the graft andplate construct in place

[0039]FIG. 21 is a top view of another embodiment of the graft and plateconstruct

[0040]FIG. 22 is a side view of the construct

[0041]FIG. 23 is a cross section of the vertebra with the graft andplate construct in place

[0042]FIG. 24 is top view of another embodiment of the plate

[0043]FIG. 25 is a side view of the plate

[0044]FIG. 26 is a cross section of the vertebra with plate in place

[0045]FIG. 27 is a side view of another embodiment of the plate

[0046]FIG. 28 is a cross section view of the vertebra with the plate inplace

[0047]FIG. 29 is a top view of another embodiment of the plate

[0048]FIG. 30 is a side view of the plate

[0049]FIG. 31 is a top view of another embodiment of the plate

[0050]FIG. 32 is a side view of the plate

[0051]FIG. 33 is a cross section of the vertebra with one embodiment ofthe plate in place

[0052]FIG. 34 is a cross section of the vertebra with another embodimentof the plate in place

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] A top view of a vertebra is illustrated in FIG. 1 with vertebralbody 1, facet 2, junctions of the facet and lamina 3 and 6, lamina 4,spinous process 5, and spinal canal 7.

[0054] In one embodiment of the bone fusion device as illustrated inFIGS. 2 and 3, the device has a rectangular configuration with a topsurface 9, longitudinal edge 8, side edge 10, and grooved edges 10 and11 to allow securement to the lamina and facet.

[0055] For the open-door technique of laminoplasty, a bicortical openingat the junction of the lamina and facet on one side and a unicorticalgroove 6 on the other side with a greenstick fracture is created for thelaminar displacement as illustrated in FIG. 4. A bone fusion graft 8 isplaced between the facet 2 and lamina 4 to maintain the repositionedshape of the laminoplasty that provides decompression of the spinalcanal 7.

[0056] In another embodiment of the bone fusion device with alongitudinal side 12 and top surface 13 as illustrated in a side view inFIG. 5, the edges at the ends are shouldered with superior cuffs 14 and16 and edge 15. Following the open-door laminoplasty, as depicted inFIG. 6, the bone fusion device rests between the lamina 4 on one sideand facet 2 on the other and the shouldered ends 14 and 16 preventmigration of the graft into the spinal canal 7.

[0057] A plate is also used following the laminoplasty to stabilize andfuse the displaced lamina in the decompressed position. The plate has atop surface 20 with several bone screw receiving holes as illustrated inFIG. 7. Screw holes at the ends 17 and 19 secure the plate to the laminaon one side and the facet on the other. Screw hole 18 in the center ofthe plate can be used to secure the bone graft to the plate. In anotherembodiment of the plate as seen in FIG. 8, there are bone receivingscrew holes 21 and 22 throughout the plate 23. As illustrated in FIG. 9,the plates have curved ends to conform to the anatomy of the laminafollowing the open door laminoplasty technique with a top surface 20 andupward curved end 24 for facet fixation and downward curved end 25 forlaminar fixation.

[0058] In order to simplify the technique of laminoplasty and providelaminar fusion as well as stabilization, a pre-assembled construct withthe plate attached to the bone fusion device is used as illustrated inFIGS. 10, 11, and 13. The plate has a top surface 27 with a curved edgepointing superiorly 30 and inferiorly 31. The bone screw holes at theboth ends 28 and 29 allow the plate to be secured to the bone withscrews. The bone fusion graft 26 has notches at the ends 32 as seen inFIG. 11, whereas in another embodiment in FIG. 13, the bone fusion graft33 has shouldered ends 35 with a superior cuff 34. The plate and fusiondevice construct is placed as seen in FIGS. 12 and 14 following anopen-door laminoplasty. The bone fusion devices either 26 or 33 restbetween the facet 2 and lamina 4 with the plate 27 secured to the laminawith a screw 37 and to the facet with a screw 36.

[0059] For the expansive laminoplasty technique as illustrated in FIG.15, the plate and bone fusion construct is used on both sides. On oneside, the bone graft 38 rests between the facet 42 and lamina 43 withthe plate 39 securing the construct, whereas on the other side, the bonegraft 40 rests between the facet 44 and lamina 45 with the plate 41securing the construct.

[0060] The trap door laminoplasty technique as shown in FIGS. 16 and 17involves removal of the spinous process and creation of unicorticallaminoplasty grooves 46 and 47 at the junction of the lamina and faceton both sides. The displaced lamina are then maintained in that positionwith a bone fusion construct 8 or 12. In one embodiment of the bonegraft and plate construct for use in this laminoplasty technique asillustrated in FIGS. 18 and 19, the plate with a top surface 51 hasdownward angled ends 52 and 53 and is attached to the bone graft 50. Theplate has bone screw receiving holes 48 and 49 that allow fixation ofthe plate to the lamina on both sides. FIG. 20 illustrates the constructin place with the laminar grooves 46 and 47, bone graft 50 and the plate51 with bone screws 62 and 63 securing the construct to the lamina.

[0061] In another embodiment of the bone graft and plate construct forthe trap door laminoplasty technique as illustrated in FIGS. 21 and 22,the plate has a top surface 59 with bone screw holes 54 and 58 forfixation to the facets and screw holes 55 and 57 for further fixation tothe lamina if needed. The plate also has curved ends 60 and 61 contouredfor fixation to the facets. The bone fusion device 56 is attached to theplate in the center. FIG. 23 illustrates the construct in place with thebone graft 56, plate 59 and the plate fixated to the facets through bonescrews 64 and 65.

[0062] For the technique of open-door laminoplasty, stabilizationwithout laminar fusion can also be undertaken with the use of the platesas illustrated in FIGS. 24, 25, and 27. The plate has a top surface 66with bone screw holes at the ends 67 and 68. The ends have a superiorlyangled curve at one end 69 and inferiorly angled at the other 70. In oneembodiment as seen on the side view in FIG. 25, there is an inferiorlypointing curved hook 72 to engage the lamina at one end and a straightappendage 71 pointing inferiorly at the other end to secure to thefacet. In another embodiment of the plate as seen in FIG. 27, there isonly one appendage pointing inferiorly 72 at the end prior to thedownward curvature of the plate. The implanted construct is seen inFIGS. 26 and 28. The plate is secured to the lamina 4 via bone screw 37and facet 2 via bone screw 36. The hook 72 secures the lamina in thedisplaced laminoplasty position. As seen in FIG. 26, the additionalstraight appendage 71 at the facet end allows the plate to rest on thefacet 2.

[0063] For the trap-door technique of laminoplasty, stabilizationwithout laminar fusion is undertaken with the use of the plates alone.In one embodiment of the plate as illustrated in FIGS. 29 and 30, theplate has a top surface 73 and screw holes at both ends 74 and 75. Theappendages 75 and 76 secure the displaced lamina and the curvatures atboth ends 74 and 77 allows attachment to the lamina. The implanted plateis shown in FIG. 33 with bone screws 87 and 88 securing it to the laminaon both sides.

[0064] In another embodiment as illustrated in FIGS. 31 and 32, theplate is curved at the ends 83 and 86. The plate has a top surface 82with bone screw holes 79 and 80 for laminar fixation and holes 78 and 81for facet fixation on both sides. The appendages 84 and 85 secure thedisplaced lamina. The implanted plate is shown in FIG. 34 with bonescrews 87 and 88 securing it to the facets on both sides.

REFERENCES

[0065] U.S. Patent Documents 6080157 Jun. 27, 2000 Cathro 6241771 Jun.5, 2001 Gresser

What I claim as my invention is:
 1. A bone stabilization device for thelamina of the spine after laminoplasty comprising an elongated platewith curvature at the ends of the longitudinal axis, downward forfixation to a lamina and upward for fixation to a facet by means of ascrew through bone screw receiving holes at each end of the said plate2. The bone stabilization device of claim 1 further including: anappendage on either end perpendicular to the longitudinal plate axis andprior to the curvature at both ends to engage between the lamina and thefacet
 3. The bone stabilization device of claim 1 further including: abone fusion device wherein said plate is attached to the bone fusiondevice in the middle with the longitudinal plate edges allowing for bonefixation
 4. A bone stabilization device of claim 1 wherein said platehas a curved appendage at one end and a straight appendage at the otherend perpendicular to the longitudinal plate axis and prior to thecurvature at both ends
 5. A bone stabilization device of claim 1 whereinsaid plate has a curved appendage at one end perpendicular to thelongitudinal plate axis and prior to the curvature
 6. A bonestabilization device of claim 1 wherein said plate has a plurality ofbone screw receiving holes throughout the plate
 7. A bone stabilizationdevice of claim 1 wherein said device is made from a biocompatiblematerial selected from the group consisting of titanium, titaniumalloys, surgical steel, polymeric material, ceramic material, resorbablematerial, polyglyconate, and hydroxyapatite
 8. A bone fusion device ofclaim 3 wherein said device is made from either bone, hydroxyapatite ora resorbable material
 9. A bone stabilization device for the lamina ofthe spine after laminoplasty comprising of an elongated plate with bonescrew receiving holes at the ends wherein said plate has a downwardcurvature at both ends to allow for fixation to the lamina via screws10. The bone stabilization device of claim 9 further including: a curvedappendage in the middle perpendicular to the longitudinal plate axis andprior to the curvature at both ends to secure the lamina
 11. The bonestabilization device of claim 9 further including: a bone fusion devicewherein said plate is attached to the bone fusion device in the middlewith the longitudinal plate edges allowing for bone fixation via bonefasteners
 12. A bone stabilization device of claim 9 wherein said platehas straight appendages in the middle perpendicular to the longitudinalplate axis and prior to the curvature at both ends
 13. A bonestabilization device of claim 9 wherein said plate has a plurality ofbone screw receiving holes throughout the plate
 14. A bone stabilizationdevice of claim 9 wherein said device is made from biocompatiblematerial selected from the group consisting of titanium, titaniumalloys, surgical steel, polymeric material, ceramic material, resorbablematerial, polyglyconate, and hydroxyapatite
 15. A bone fusion device ofclaim 11 wherein said device is made from either bone, hydroxyapatite,or a resorbable material
 16. A bone stabilization device of claim 9further including: a L-shaped curvature at the end on both sides toallow for fixation to the facets by means of bone fasteners
 17. A spacerfor the lamina of the spine after laminoplasty comprising of arectangular shape with concave curved edges contoured at thelongitudinal ends to allow for engagement between the lamina
 18. Aspacer for the lamina of the spine after laminoplasty comprising of arectangular shape wherein both edges at the end of the longitudinal axisof the said spacer have a superior cuff to allow for engagement betweenthe lamina
 19. A spacer of claim 17 wherein said device is made fromeither bone, hydroxyapatite, or a biocompatible material suitable forbone fusion
 20. A spacer of claim 18 wherein said device is made fromeither bone, hydroxyapatite, or a biocompatible material suitable forbone fusion
 21. A method of stabilizing and fusing the reshaped laminaafter a laminoplasty comprising the steps of: displacing the severededge of a lamina at the junction of the lamina and facet, providing aspacing means with the edges of the said spacing means contoured toengage the lamina at one end and the facet at the other end, and afixation means attached to the said spacing means in the middle withcurvatures at both ends in opposing directions allowing bone screwplacement through one end of the said fixation means to the lamina andbone screw placement through the other end of the said fixation means tothe facet
 22. A method of stabilizing the reshaped lamina after alaminoplasty comprising the steps of: displacing the severed edge of thelamina at the junction of the lamina and facet, a fixation meanscomprising of a plate with appendages at either ends prior to thecurvature of the longitudinal axis of the said fixation means to securethe lamina on one side and the facet on the other and maintain theirrepositioned shape along with fixation of the plate to the lamina andfacet via bone fasteners
 23. A method of stabilizing and fusing therepositioned lamina after a laminoplasty comprising the steps of:displacing the severed edges of lamina at the junction of the lamina andfacet on both sides, providing a spacing means with the edges of thesaid spacing means contoured to engage between the lamina and facet onboth sides of the vertebra, a fixation means with the said spacing meansattached in the middle contoured to allow bone screw placement throughone end of the said fixation means to the lamina and bone screwplacement through the other end of the said fixation means to the faceton both sides of the vertebra
 24. A method of stabilizing and fusing thereshaped lamina after a laminoplasty comprising the steps of: displacingboth lamina through severed edges in the middle, providing a spacingmeans with the edges of the spacing means contoured to engage thedisplaced lamina at both ends, and a fixation means comprising of aplate with the said spacing means attached at the middle of the fixationmeans and the said fixation means comprising of a curvature at both endsof the longitudinal axis to secure the lamina and/or facets on bothsides with bone fasteners
 25. A method of stabilizing the reshapedlamina after a laminoplasty comprising the steps of: displacing bothlamina through severed edges in the middle, providing fixation meanscomprising of a plate with two appendages perpendicular to thelongitudinal axis of the said fixation means spaced apart in the middleto engage the lamina on either side with the said fixation means alsocomprising of curvatures at both ends to secure the fixation means tothe lamina and/or facets on both sides with bone fasteners